/*
 * jidctred.c
 *
 * Copyright (C) 1994, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains inverse-DCT routines that produce reduced-size output:
 * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
 *
 * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
 * algorithm used in jidctint.c.  We simply replace each 8-to-8 1-D IDCT step
 * with an 8-to-4 step that produces the four averages of two adjacent outputs
 * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
 * These steps were derived by computing the corresponding values at the end
 * of the normal LL&M code, then simplifying as much as possible.
 *
 * 1x1 is trivial: just take the DC coefficient divided by 8.
 *
 * See jidctint.c for additional comments.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"				/* Private declarations for DCT subsystem */

#ifdef IDCT_SCALING_SUPPORTED


/*
 * This module is specialized to the case DCTSIZE = 8.
 */

#if DCTSIZE != 8
Sorry, this code only copes with 8 x8 DCTs.	/* deliberate syntax err */
#endif
/* Scaling is the same as in jidctint.c. */
#if BITS_IN_JSAMPLE == 8
#define CONST_BITS  13
#define PASS1_BITS  2
#else
#define CONST_BITS  13
#define PASS1_BITS  1			/* lose a little precision to avoid overflow */
#endif
/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
 * causing a lot of useless floating-point operations at run time.
 * To get around this we use the following pre-calculated constants.
 * If you change CONST_BITS you may want to add appropriate values.
 * (With a reasonable C compiler, you can just rely on the FIX() macro...)
 */
#if CONST_BITS == 13
#define FIX_0_211164243  ((INT32)  1730)	/* FIX(0.211164243) */
#define FIX_0_509795579  ((INT32)  4176)	/* FIX(0.509795579) */
#define FIX_0_601344887  ((INT32)  4926)	/* FIX(0.601344887) */
#define FIX_0_720959822  ((INT32)  5906)	/* FIX(0.720959822) */
#define FIX_0_765366865  ((INT32)  6270)	/* FIX(0.765366865) */
#define FIX_0_850430095  ((INT32)  6967)	/* FIX(0.850430095) */
#define FIX_0_899976223  ((INT32)  7373)	/* FIX(0.899976223) */
#define FIX_1_061594337  ((INT32)  8697)	/* FIX(1.061594337) */
#define FIX_1_272758580  ((INT32)  10426)	/* FIX(1.272758580) */
#define FIX_1_451774981  ((INT32)  11893)	/* FIX(1.451774981) */
#define FIX_1_847759065  ((INT32)  15137)	/* FIX(1.847759065) */
#define FIX_2_172734803  ((INT32)  17799)	/* FIX(2.172734803) */
#define FIX_2_562915447  ((INT32)  20995)	/* FIX(2.562915447) */
#define FIX_3_624509785  ((INT32)  29692)	/* FIX(3.624509785) */
#else
#define FIX_0_211164243  FIX(0.211164243)
#define FIX_0_509795579  FIX(0.509795579)
#define FIX_0_601344887  FIX(0.601344887)
#define FIX_0_720959822  FIX(0.720959822)
#define FIX_0_765366865  FIX(0.765366865)
#define FIX_0_850430095  FIX(0.850430095)
#define FIX_0_899976223  FIX(0.899976223)
#define FIX_1_061594337  FIX(1.061594337)
#define FIX_1_272758580  FIX(1.272758580)
#define FIX_1_451774981  FIX(1.451774981)
#define FIX_1_847759065  FIX(1.847759065)
#define FIX_2_172734803  FIX(2.172734803)
#define FIX_2_562915447  FIX(2.562915447)
#define FIX_3_624509785  FIX(3.624509785)
#endif
/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
 * For 8-bit samples with the recommended scaling, all the variable
 * and constant values involved are no more than 16 bits wide, so a
 * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
 * For 12-bit samples, a full 32-bit multiplication will be needed.
 */
#if BITS_IN_JSAMPLE == 8
#define MULTIPLY(var,const)  MULTIPLY16C16(var,const)
#else
#define MULTIPLY(var,const)  ((var) * (const))
#endif
/* Dequantize a coefficient by multiplying it by the multiplier-table
 * entry; produce an int result.  In this module, both inputs and result
 * are 16 bits or less, so either int or short multiply will work.
 */
#define DEQUANTIZE(coef,quantval)  (((ISLOW_MULT_TYPE) (coef)) * (quantval))
/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 4x4 output block.
 */
GLOBAL void
jpeg_idct_4x4(j_decompress_ptr cinfo, jpeg_component_info * compptr,
			  JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
{
	INT32           tmp0, tmp2, tmp10, tmp12;
	INT32           z1, z2, z3, z4;
	JCOEFPTR        inptr;
	ISLOW_MULT_TYPE *quantptr;
	int            *wsptr;
	JSAMPROW        outptr;
	JSAMPLE        *range_limit = IDCT_range_limit(cinfo);
	int             ctr;
	int             workspace[DCTSIZE * 4];	/* buffers data between passes */

	SHIFT_TEMPS
		/* Pass 1: process columns from input, store into work array. */
		inptr = coef_block;
	quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	wsptr = workspace;
	for(ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--)
	{
		/* Don't bother to process column 4, because second pass won't use it */
		if(ctr == DCTSIZE - 4)
			continue;
		if((inptr[DCTSIZE * 1] | inptr[DCTSIZE * 2] | inptr[DCTSIZE * 3] |
			inptr[DCTSIZE * 5] | inptr[DCTSIZE * 6] | inptr[DCTSIZE * 7]) == 0)
		{
			/* AC terms all zero; we need not examine term 4 for 4x4 output */
			int             dcval = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]) << PASS1_BITS;

			wsptr[DCTSIZE * 0] = dcval;
			wsptr[DCTSIZE * 1] = dcval;
			wsptr[DCTSIZE * 2] = dcval;
			wsptr[DCTSIZE * 3] = dcval;

			continue;
		}

		/* Even part */

		tmp0 = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]);
		tmp0 <<= (CONST_BITS + 1);

		z2 = DEQUANTIZE(inptr[DCTSIZE * 2], quantptr[DCTSIZE * 2]);
		z3 = DEQUANTIZE(inptr[DCTSIZE * 6], quantptr[DCTSIZE * 6]);

		tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, -FIX_0_765366865);

		tmp10 = tmp0 + tmp2;
		tmp12 = tmp0 - tmp2;

		/* Odd part */

		z1 = DEQUANTIZE(inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7]);
		z2 = DEQUANTIZE(inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5]);
		z3 = DEQUANTIZE(inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3]);
		z4 = DEQUANTIZE(inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1]);

		tmp0 = MULTIPLY(z1, -FIX_0_211164243)	/* sqrt(2) * (c3-c1) */
			+ MULTIPLY(z2, FIX_1_451774981)	/* sqrt(2) * (c3+c7) */
			+ MULTIPLY(z3, -FIX_2_172734803)	/* sqrt(2) * (-c1-c5) */
			+ MULTIPLY(z4, FIX_1_061594337);	/* sqrt(2) * (c5+c7) */

		tmp2 = MULTIPLY(z1, -FIX_0_509795579)	/* sqrt(2) * (c7-c5) */
			+ MULTIPLY(z2, -FIX_0_601344887)	/* sqrt(2) * (c5-c1) */
			+ MULTIPLY(z3, FIX_0_899976223)	/* sqrt(2) * (c3-c7) */
			+ MULTIPLY(z4, FIX_2_562915447);	/* sqrt(2) * (c1+c3) */

		/* Final output stage */

		wsptr[DCTSIZE * 0] = (int)DESCALE(tmp10 + tmp2, CONST_BITS - PASS1_BITS + 1);
		wsptr[DCTSIZE * 3] = (int)DESCALE(tmp10 - tmp2, CONST_BITS - PASS1_BITS + 1);
		wsptr[DCTSIZE * 1] = (int)DESCALE(tmp12 + tmp0, CONST_BITS - PASS1_BITS + 1);
		wsptr[DCTSIZE * 2] = (int)DESCALE(tmp12 - tmp0, CONST_BITS - PASS1_BITS + 1);
	}

	/* Pass 2: process 4 rows from work array, store into output array. */

	wsptr = workspace;
	for(ctr = 0; ctr < 4; ctr++)
	{
		outptr = output_buf[ctr] + output_col;
		/* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
		if((wsptr[1] | wsptr[2] | wsptr[3] | wsptr[5] | wsptr[6] | wsptr[7]) == 0)
		{
			/* AC terms all zero */
			JSAMPLE         dcval = range_limit[(int)DESCALE((INT32) wsptr[0], PASS1_BITS + 3) & RANGE_MASK];

			outptr[0] = dcval;
			outptr[1] = dcval;
			outptr[2] = dcval;
			outptr[3] = dcval;

			wsptr += DCTSIZE;	/* advance pointer to next row */
			continue;
		}
#endif

		/* Even part */

		tmp0 = ((INT32) wsptr[0]) << (CONST_BITS + 1);

		tmp2 = MULTIPLY((INT32) wsptr[2], FIX_1_847759065) + MULTIPLY((INT32) wsptr[6], -FIX_0_765366865);

		tmp10 = tmp0 + tmp2;
		tmp12 = tmp0 - tmp2;

		/* Odd part */

		z1 = (INT32) wsptr[7];
		z2 = (INT32) wsptr[5];
		z3 = (INT32) wsptr[3];
		z4 = (INT32) wsptr[1];

		tmp0 = MULTIPLY(z1, -FIX_0_211164243)	/* sqrt(2) * (c3-c1) */
			+ MULTIPLY(z2, FIX_1_451774981)	/* sqrt(2) * (c3+c7) */
			+ MULTIPLY(z3, -FIX_2_172734803)	/* sqrt(2) * (-c1-c5) */
			+ MULTIPLY(z4, FIX_1_061594337);	/* sqrt(2) * (c5+c7) */

		tmp2 = MULTIPLY(z1, -FIX_0_509795579)	/* sqrt(2) * (c7-c5) */
			+ MULTIPLY(z2, -FIX_0_601344887)	/* sqrt(2) * (c5-c1) */
			+ MULTIPLY(z3, FIX_0_899976223)	/* sqrt(2) * (c3-c7) */
			+ MULTIPLY(z4, FIX_2_562915447);	/* sqrt(2) * (c1+c3) */

		/* Final output stage */

		outptr[0] = range_limit[(int)DESCALE(tmp10 + tmp2, CONST_BITS + PASS1_BITS + 3 + 1) & RANGE_MASK];
		outptr[3] = range_limit[(int)DESCALE(tmp10 - tmp2, CONST_BITS + PASS1_BITS + 3 + 1) & RANGE_MASK];
		outptr[1] = range_limit[(int)DESCALE(tmp12 + tmp0, CONST_BITS + PASS1_BITS + 3 + 1) & RANGE_MASK];
		outptr[2] = range_limit[(int)DESCALE(tmp12 - tmp0, CONST_BITS + PASS1_BITS + 3 + 1) & RANGE_MASK];

		wsptr += DCTSIZE;		/* advance pointer to next row */
	}
}


/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 2x2 output block.
 */

GLOBAL void
jpeg_idct_2x2(j_decompress_ptr cinfo, jpeg_component_info * compptr,
			  JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
{
	INT32           tmp0, tmp10, z1;
	JCOEFPTR        inptr;
	ISLOW_MULT_TYPE *quantptr;
	int            *wsptr;
	JSAMPROW        outptr;
	JSAMPLE        *range_limit = IDCT_range_limit(cinfo);
	int             ctr;
	int             workspace[DCTSIZE * 2];	/* buffers data between passes */

	SHIFT_TEMPS
		/* Pass 1: process columns from input, store into work array. */
		inptr = coef_block;
	quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	wsptr = workspace;
	for(ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--)
	{
		/* Don't bother to process columns 2,4,6 */
		if(ctr == DCTSIZE - 2 || ctr == DCTSIZE - 4 || ctr == DCTSIZE - 6)
			continue;
		if((inptr[DCTSIZE * 1] | inptr[DCTSIZE * 3] | inptr[DCTSIZE * 5] | inptr[DCTSIZE * 7]) == 0)
		{
			/* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
			int             dcval = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]) << PASS1_BITS;

			wsptr[DCTSIZE * 0] = dcval;
			wsptr[DCTSIZE * 1] = dcval;

			continue;
		}

		/* Even part */

		z1 = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]);
		tmp10 = z1 << (CONST_BITS + 2);

		/* Odd part */

		z1 = DEQUANTIZE(inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7]);
		tmp0 = MULTIPLY(z1, -FIX_0_720959822);	/* sqrt(2) * (c7-c5+c3-c1) */
		z1 = DEQUANTIZE(inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5]);
		tmp0 += MULTIPLY(z1, FIX_0_850430095);	/* sqrt(2) * (-c1+c3+c5+c7) */
		z1 = DEQUANTIZE(inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3]);
		tmp0 += MULTIPLY(z1, -FIX_1_272758580);	/* sqrt(2) * (-c1+c3-c5-c7) */
		z1 = DEQUANTIZE(inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1]);
		tmp0 += MULTIPLY(z1, FIX_3_624509785);	/* sqrt(2) * (c1+c3+c5+c7) */

		/* Final output stage */

		wsptr[DCTSIZE * 0] = (int)DESCALE(tmp10 + tmp0, CONST_BITS - PASS1_BITS + 2);
		wsptr[DCTSIZE * 1] = (int)DESCALE(tmp10 - tmp0, CONST_BITS - PASS1_BITS + 2);
	}

	/* Pass 2: process 2 rows from work array, store into output array. */

	wsptr = workspace;
	for(ctr = 0; ctr < 2; ctr++)
	{
		outptr = output_buf[ctr] + output_col;
		/* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
		if((wsptr[1] | wsptr[3] | wsptr[5] | wsptr[7]) == 0)
		{
			/* AC terms all zero */
			JSAMPLE         dcval = range_limit[(int)DESCALE((INT32) wsptr[0], PASS1_BITS + 3) & RANGE_MASK];

			outptr[0] = dcval;
			outptr[1] = dcval;

			wsptr += DCTSIZE;	/* advance pointer to next row */
			continue;
		}
#endif

		/* Even part */

		tmp10 = ((INT32) wsptr[0]) << (CONST_BITS + 2);

		/* Odd part */

		tmp0 = MULTIPLY((INT32) wsptr[7], -FIX_0_720959822)	/* sqrt(2) * (c7-c5+c3-c1) */
			+ MULTIPLY((INT32) wsptr[5], FIX_0_850430095)	/* sqrt(2) * (-c1+c3+c5+c7) */
			+ MULTIPLY((INT32) wsptr[3], -FIX_1_272758580)	/* sqrt(2) * (-c1+c3-c5-c7) */
			+ MULTIPLY((INT32) wsptr[1], FIX_3_624509785);	/* sqrt(2) * (c1+c3+c5+c7) */

		/* Final output stage */

		outptr[0] = range_limit[(int)DESCALE(tmp10 + tmp0, CONST_BITS + PASS1_BITS + 3 + 2) & RANGE_MASK];
		outptr[1] = range_limit[(int)DESCALE(tmp10 - tmp0, CONST_BITS + PASS1_BITS + 3 + 2) & RANGE_MASK];

		wsptr += DCTSIZE;		/* advance pointer to next row */
	}
}


/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 1x1 output block.
 */

GLOBAL void
jpeg_idct_1x1(j_decompress_ptr cinfo, jpeg_component_info * compptr,
			  JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
{
	int             dcval;
	ISLOW_MULT_TYPE *quantptr;
	JSAMPLE        *range_limit = IDCT_range_limit(cinfo);

	SHIFT_TEMPS
		/* We hardly need an inverse DCT routine for this: just take the
		 * average pixel value, which is one-eighth of the DC coefficient.
		 */
		quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
	dcval = (int)DESCALE((INT32) dcval, 3);

	output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
}

#endif							/* IDCT_SCALING_SUPPORTED */
